Abnormal breathing may be treated by applying a breathing gas under positive pressure to a patient's airway via a positive airway pressure (PAP) device. This positive pressure may effectively “splint” the airway, thereby maintaining an open passage to the lungs. The pressure of the breathing gas delivered to the patient may be desired to be kept relatively constant at a desired or prescribed pressure during positive pressure therapy. This therapy technique is commonly referred to as continuous positive airway pressure (CPAP). CPAP therapy may be provided using either open-loop or closed-loop control. CPAP therapy may be provided at a constant or continuously positive target pressure using a control unit that controls breathing gas pressure based on the fixed target pressure. Alternatively, the CPAP therapy may also be controlled using a softened exhalation target pressure (SoftX™). SoftX™ is a trademark of Invacare Corporation. In SoftX™, the breathing gas is delivered at a relatively constant pressure, like CPAP, and during an initial portion of exhalation, the pressure set point is reduced, but then increases toward the constant pressure during the latter portion of exhalation, to help maintain the positive airway pressure.
In another type of positive pressure therapy, the pressure of the breathing gas delivered to the patient may be varied with the patient's breathing cycle or varied with the patient's effort such that the pressure during exhalation is less than the pressure during inhalation. This therapy technique may increase comfort to the patient during the therapy and is commonly referred to as bi-level positive airway pressure (BiPAP). In another type of positive pressure therapy, the pressure of the breathing gas delivered to the patient is varied in proportion to the flow generated by the patient. This therapy technique is commonly referred to as proportional positive airway pressure (PPAP).
Any of the various types of PAP devices may also incorporate ramping of the positive pressure from a lower pressure level to a higher desired or prescribed pressure level over an extended period (e.g., 10-15 minutes). This ramping process is intended to reduce the airway pressure while the patient is awake and for a period during which the patient may be expected to fall asleep. The positive airway pressure reaches the desired or prescribed level as the ramping period expires.